A. Technical Field
The present invention relates to a high molecular polyetherpolyester and its production process and use, especially, use for films.
B. Background Art
Conventionally, high molecular polyetherpolyesters are used for various purposes, for example, for packing materials by molding the high molecular polyetherpolyester alone or combinations thereof with various additives into sheets or films. It is known that where the high molecular polyetherpolyester is molded into a film, important mechanical properties of the film generally greatly depend on the molecular weight of the high molecular polyetherpolyester. Therefore, the below-mentioned various production processes are studied.
For example, if alicyclic alkylene oxides such as ethylene oxide is subjected to ring-opening polymerization using catalysts such as organometallic complexes, high molecular polyalkylene oxides having polyether structures are obtained. It is possible to obtain a polyalkylene oxide having a molecular weight of several million or more by this process, but at present a process for producing industrially a polyalkylene oxide having a molecular weight of 100,000 to 1,000,000 (such a polyalkylene oxide is assumed to have good moldability) with good efficiency has not yet been found.
In addition, a process is known in which: either or both of ethylene oxide and propylene oxide are subjected to ring-opening polymerization using basic catalysts, for example, comprising either or both of sodium hydroxide and potassium hydroxide, to obtain a low molecular polyalkylene oxide, which is then reacted with various chain-extending agents to convert the polyalkylene oxide into a high molecular one, thus obtaining a high molecular polyetherpolyester. An example of such a process, in which carboxylic diesters are used as the chain-extending agents, is disclosed in Japanese Allowable Patent Publication (Kokoku) No. 5-68493. The molecular weight of the high molecular polyetherpolyester resultant from this process reaches 100,000 or more, but a film of this high molecular polyetherpolyester is very brittle and merely has an elongation of 100% or less. In addition, in the process as mentioned immediately above, because the reaction is run by condensation, an alcohol forms as a by-product, and the system of reaction accordingly needs to be put under vacuum to remove the alcohol. Therefore, high costs for vacuum facilities and for recovering and treating condensation products are needed, and the production efficiency is low.
An example of the process, in which diisocyanates are used as the chain-extending agents, is disclosed in Japanese Patent Application Publication (Kokai) No. 6-32976. Polyurethane resin resultant from this process has so good mechanical strength that the polyurethane resin can be mold-processed, but this polyurethane resin has a problem in that the diisocyanate, which is used for the chain extension reaction, is very toxic. Because there is a danger that the diisocyanate might remain in products, the range of the use of this polyurethane resin is limited to an extremely narrow range. In addition, because the diisocyanate has high reactivity, the reaction thereof is difficult to control, and it is difficult to manage production process steps and the quality of products.
Furthermore, examples of the process to solve the above-mentioned problems are disclosed in (1) Japanese Patent Application Publication (Kokai) No. 58-179227, (2) Japanese Allowable Patent Publication (Kokoku) No. 1-15532, and (3) Polymer, 1973, Vol. 14, October, pp. 466-468, in which acid anhydrides are used as the chain-extending agents. The process as disclosed in document (1) above is a process for producing a high molecular polyetherpolyester from pyromellitic dianhydride and a low molecular polyalkylene oxide. The process as disclosed in document (2) above is a process for producing a high molecular polyether-ester copolymer from polyether, of which both terminal ends are hydroxyl groups, using trimellitic anhydride as a branching agent. The process as disclosed in document (3) above is a process for producing a high molecular polyetherpolyester from poly(propylene glycol) and pyromellitic dianhydride.
The high molecular polyetherpolyesters, as obtained by processes (1) to (3) above, all have problems in that their mechanical strength is not high. As to process (1) above, for example, a film of the resultant high molecular polyetherpolyester merely has a tensile strength of less than 80 kgf/cm.sup.2 and an elongation of less than 100%, and is very brittle. Also as to process (2) above, the mechanical strength of the resultant high molecular polyetherpolyester is not high. As to process (3) above, the molecular weight only increases to such a degree that an intrinsic viscosity of about 1.6 kg/m.sup.3 is displayed, and the resultant molecular weight is not very high.
Where the high molecular polyetherpolyester is produced by the above-mentioned conventional processes, the increase of the molecular weight involves the increase of the viscosity during the production. Where a solvent is used to suppress the increase of the viscosity, a step for removing the solvent is needed at the end of the reaction. Therefore, such a process is not industrially efficient. Where the reaction is carried out at or above a high temperature of 200.degree. C. to suppress the increase of the viscosity, thermal deterioration of the polymer often occurs in the reaction system. The prevention of the thermal deterioration needs expensive additives such as antioxidants, and such a process is not industrially efficient, either.
On the other hand, where the high molecular polyetherpolyester is handled as an industrial product, its form is very important. The shipment form as the industrial product depends on various use purposes, but examples thereof are: (1) a liquid such as a solution of water or an organic solvent; (2) a lump; (3) a powder or flake; (4) a pellet.
Form (1) above might be suitable dependently on use purposes, but has problems in that: the transportation cost increases, or the dissolution consumes time or deteriorates the stability to the passage of time, or the storage needs a wide area. Form (2) above is not industrially very common use form, so the use method is limited. In addition, there is a problem in that automation is difficult. Form (3) above is obtained by mechanically pulverizing the lump and is bearable to various use purposes, but has problems in the step of making a powder or flake. Some high molecular polyetherpolyesters have a glass transition temperature of 0.degree. C. or lower. Therefore, the pulverization of such polyetherpolyesters must be carried out by freeze pulverization that needs freezing-media such as liquid nitrogen or dry ice. Therefore, form (3) provides very bad results with regard to the production efficiency and is therefore not suitable for mass production. In contrast therewith, form (4) above is flexibly correspondable to various use purposes and the most common use form as a medium for molding a thermoplastic resin. In addition, form (4) saves the transportation cost and is advantageous to the storage. However, where the high molecular polyetherpolyester is produced with conventional reaction apparatuses for high viscosity, the production in the form of a pellet is difficult.